In off-road driving such as motocross, when running through an unlevel land, the rider may receive large vibration through the motorcycle or take a large action to maintain the balance of the motorcycle, and hence the amount of exercise of the rider is large. Therefore, conditions that should be considered by the rider when selecting a helmet include being lightweight, facilitating breathing, providing a large view, ensuring coolness, and the like.
As a helmet that satisfies the above conditions, conventionally, a so-called jet-type helmet through which the rider's face is open largely is used. With the jet-type helmet, however, it is difficult to protect the rider's chin effectively. Hence, as the helmet manufacturing technique improved afterwards, a full-face-type helmet which is lightweight, facilitates breathing and provides a large view, thus suitable for off-road driving of, e.g., a motocross has appeared. Such an off-road driving full-face-type helmet is disclosed in, e.g., U.S. Pat. No. 4,555,816.
The off-road driving full-face-type helmet disclosed in U.S. Pat. No. 4,555,816 comprises a large opening at the center of the chin cover to supply external air to near the wearer's mouth. In the helmet of U.S. Pat. No. 4,555,816, in order to introduce external air to the wearer's head as well, small openings for introducing external air into the head cover are provided to the left and right sides, respectively, of the large opening described above.
Furthermore, in the full-face-type helmet of U.S. Pat. No. 4,555,816, air passages to relatively move the external air from the small openings in the chin cover to inside the head cover are formed between an outer shall integrally molded of the chin cover and head cover, and an impact-on-the-chin absorbing liner for the chin cover and an impact-on-the-head absorbing liner for the head cover. More specifically, ventilation ridge grooves are formed in the outer surfaces of the impact-on-the-chin absorbing liner and impact-on-the-head absorbing liner, respectively, to substantially communicate with each other, thereby forming the air passage comprising the ventilation ridge grooves and the outer shell disposed outside them.
In the full-face-type helmet of U.S. Pat. No. 4,555,816 having the above arrangement, an external air introducing through hole extending through the impact-on-the-head absorbing liner in the direction of thickness must be formed near the side head region of the impact-on-the-head absorbing liner in order to introduce external air into the interior of the impact-on-the-head absorbing liner (that is, a head accommodating space of the helmet) through the terminal end portion of the air passage. Also, the air passage as described above is formed to introduce external air into the head cover through small openings formed in the chin cover. In the air passage, external air that has flown for a comparatively long distance along the ventilation ridge grooves formed in the outer surfaces of the impact-on-the-chin absorbing liner and impact-on-the-head absorbing liner, respectively, must bend substantially at a right angle at the through hole. As the resistance against the external air flow is large, the external air cannot flow well from the small openings formed in the chin cover into the head cover.
Hence, in the full-face-type helmet of U.S. Pat. No. 4,555,816, ventilation in the full-face-type helmet is not performed well unless the driving speed of the motorcycle is maintained at a certain degree. In the driving state wherein the driving speed is comparatively low and the amount of exercise of the rider is comparatively large, as in a case wherein the rider runs through an unlevel land on a motorcycle, ventilation of the interior of the full-face-type helmet is not performed well. Consequently, vapor generated by perspiration of the rider's head fills the interior of the full-face-type helmet to increase the unpleasantness of the rider as the wearer.
In the full-face-type helmet of U.S. Pat. No. 4,555,816, the impact-on-the-head absorbing liner must moderate the impact acting on the helmet by absorbing it while deforming. If the through hole extending through the impact-on-the-head absorbing liner in the direction of the thickness is formed near the side head region of the impact-on-the-head absorbing liner, the performance of moderating the impact may degrade near the side head region of the impact-on-the-head absorbing liner provided with the through hole. Hence, the through hole extending through the impact-on-the-head absorbing liner in the direction of thickness is largely restricted in its size and position.
Hence, according to the present invention, the defects as described above of the conventional full-face-type helmet such as an off-road driving helmet can be corrected effectively with a comparatively simple arrangement.